Optical filter

ABSTRACT

An optical filter containing at least a clay mineral complex (A). The clay mineral complex (A) comprises a layered clay mineral (B) intercalated with a dye cation (C), and an organic cation (D).

TECHNICAL FIELD

This invention relates to an optical filter containing aninorganic/organic complex having a layered clay mineral intercalatedwith dye cations and organic cations and optionally containing a binderresin. The optical filter is specially suited for application to imagedisplays.

BACKGROUND ART

Compounds having an intense absorption of specific wavelengths of lightare used in a recording layer of optical recording media, such as CD-Rs,DVD-Rs, DVD+Rs, and blue laser recording discs, and an optical elementof image displays, such as liquid crystal displays (LCDs), plasmadisplay panels (PDPs), electroluminescence displays (ELDs), cathode raytubes (CRTs), vacuum fluorescent displays (VFDs), and field emissiondisplays (FEDs).

The optical element of an image display is exemplified by a lightabsorber used in a color filter having a substrate and color pixelsformed on the substrate and transmitting white light to convert amonochromatic display to a color display. An image display achieves afull color display using combinations of three primary colors of light,red, blue, and green. Light for displaying a color image contains acomponent that causes display quality reduction, such as light raysbetween green and red (550 to 600 nm) and a component that causesmalfunction of an infrared remote controller (750 to 1100 nm). On theother hand, it is required with an image display that the unnecessarylight component be selectively absorbed by an optical filter to achievea color display or to eliminate the malfunction of an infrared remotecontroller. Absorption of light with wavelengths of from 480 to 500 nmand of from 540 to 560 nm is also demanded in order to preventreflection of ambient light, such as a fluorescent lamp. Then, an imagedisplay is equipped with an optical filter containing a light absorbingcompound (light absorber) capable of selectively absorbing light of thewavelengths recited separately from the color filter.

A conventional optical filter is manufactured by affixing an opticalfilm containing a light absorbing compound (light absorber) capable ofselectively absorbing specific wavelengths of light to a transparentsubstrate, such as a glass plate, via a pressure-sensitive adhesive.Thus, there have been problems of high cost due to many steps involvedin the manufacture and difficulty in reducing the thickness of theoptical filter.

Patent Document 1 discloses a film for an electronic display, thepressure sensitive adhesive layer of which film contains a dye andcarbon black. Patent Document 2 discloses a pressure-sensitive adhesivecontaining a dye. Patent Document 3 proposes a filter for a display, thepressure sensitive adhesive layer of which contains a dye.

It is difficult, however, to control deterioration of a dye compound inan adhesive layer caused by light, heat or the like. An optical filterthat maintains sufficient optical characteristics is not available todate.

Patent Document 4 discloses an aqueous ink containing a colorant havingclay intercalated with a dye. Patent Document 5 discloses a clay mineralcomplex having a layered clay mineral intercalated with organic cationsand an intercalant. Patent Document 6 discloses a fluorescent layeredinorganic/organic complex of an anion-exchanging, inorganic layercompound having carried thereon an aliphatic quaternary ammonium ion andan anionic laser dye. These patent documents are silent to applying thecolorant or the colored complex to an optical filter or improving moistheat resistance of an optical filter by using the colorant or the claymineral complex.

Patent Document 1: JP 2003-82302A

Patent Document 2: JP 2004-107566A

Patent Document 3: Japanese Patent 3311720

Patent Document 4: JP 10-77427A

Patent Document 5: JP 2-293315A

Patent Document 6: JP 2004-2491A

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

Applicant has filed an application for patent on an invention relatingto an optical filter containing a mixture of a dye compound and alayered clay mineral (WO2006/137272A1).

When the mixture of the dye compound and the layered clay mineral isused in an optical filter as such without being once isolated as a claymineral complex and dried, the resulting optical filter contains anorganic solvent-insoluble component, such as a quaternary ammonium salt,which can reduce moist heat resistance of the filter. Furthermore, ionexchange of the interlayer organic cations of a layered clay mineralwith dye cations is less likely to take place, raising the need toincrease the amount of the layered clay mineral to be used. This resultsin thickening a coating composition, flocculation of the clay mineralcomplex particles, or increasing the cost.

Accordingly, an object of the invention is to provide an optical filterexhibiting high resistant against light and moist heat even in itspressure-sensitive adhesive layer.

Means for Solving the Problem

As a result of extensive investigation, the inventors have found thatthe above object is accomplished by using a clay mineral complexcomprising a layered clay mineral having dye cations and organic cationsintercalated therein particularly in a pressure-sensitive adhesive layerof an optical filter.

Based on the above finding, the invention provides an optical filtercontaining at least a clay mineral complex (A). The clay mineral complex(A) comprises a layered clay mineral (B) intercalated with a dye cation(C) and an organic cation (D).

BEST MODE FOR CARRYING OUT THE INVENTION

The optical filter according to the invention will be described withreference to its preferred embodiments.

The optical filter of the invention contains at least a clay mineralcomplex (A). The clay mineral complex (A) comprises a layered claymineral (B) intercalated with a dye cation (C) and an organic cation(D).

The layered clay mineral as component (B) may be a naturally occurringsubstance, a chemically synthesized product, a clay mineral containinglithium, sodium, calcium, or like ions between its layers, or asubstitution product or a derivative or a mixture of these substances.Examples of the layered clay mineral (B) include smectite minerals,kaolin minerals, mica minerals, talc, chlorite, hydrotalcite,vermiculite, and fluorovermiculite. Examples of the smectite mineralsinclude hectorite, saponite, stevensite, beidellite, montmorillonite,bentonite, and nontronite. Examples of the kaolin minerals includekaolinite, halloysite, nacrite, dickite, chrysotile, lizardite, amesite,and pyrophyllite. Examples of the mica minerals includeLi-fluoro-taeiniolite, Na-fluoro-taeiniolite, and syntheticNa-tetrasilicic fluoromica. Among them, smectite minerals and micaminerals are preferred because of their high functionality.

Preferred of the smectite minerals are those having been purified to befree from impurities. Still preferred are lipophilic smectite havinghigh affinity to polymer binders and organic solvents. The lipophilicsmectite is obtained by lipophilizing the recited smectite mineral with,e.g., quaternary ammonium ions. Accordingly, in the cases where alipophilic smectite is used, the organic cation hereinafter described ascomponent (D) already exists in the lipophilic smectite as an interlayercation.

Commercially available products may be used as smectite, includingLucentite SWN and SWF (hydrophilic smectite, available from CO—OPChemical Co., Ltd.); Lucentite STN, STN-α, SPN, SEN, SAN, SAN2C, SAN210,STF, SSN, SSN-A, SAN312-A, SAN2C-A, and SAN210-A smectite, from CO—OPChemical Co., Ltd.); Kunipia T (montmorillonite, from KunimineIndustries Co., Ltd.); S-Ben N-400 and N-400FP (montmorillonite, fromHojun Co., Ltd.); and Benton (from Toshin Chemicals Co., Ltd.).Preferred among them are STN-A, SSN-A, SAN210-A, SAN-312-A, and SAN2Ceach of which has been purified to be freed from impurities because theyare less likely to flocculate when formulated into a clay mineralcomplex and therefore exhibit good dispersibility.

Preferred of the mica minerals are those having been purified to be freefrom impurities. Swellable mica minerals having high affinity to polymerbinders and organic solvents are still preferred.

The mica mineral may be a commercially available product, which includesSomacif (swellable mica, available from CO-OP Chemical Co., Ltd) andMicromica (non-swellable mica, from CO-OP Chemical Co., Ltd.).

The dye cation as component (C) may be a cation of any known compoundthat has been used in conventional optical filters, such as a cyaninecompound. A cation of a single species or a combination of cations oftwo or more species can be used.

Examples of the dye cation (C) include those of cyanine compounds,diimmonium compounds, aminium compounds, metal salts of azo compounds,azomethine dye compounds, triarylmethane dye compounds, naphthalimidecompounds, naphtholactam compounds, oxazine compounds, thiazinecompounds, azaxanthene compounds, quinoline compounds, indamine dyecompounds, rhodamine dye compounds, squarylium compounds, and styryl dyecompounds. In particular, a cation of a cyanine compound and a cation ofa diimmonium compound are preferred; for a clay mineral complex havingthe cation intercalated therein is not easily susceptible to theinfluence of external factors, such as ultraviolet light and moisture,and therefore exhibits high resistance to light and moist heat.Furthermore, the clay mineral complex having the cation of a cyaninecompound or a diimmonium compound has high affinity to an organicsolvent with low polarity. Two or more kinds of the dye cations may beused as component (C).

The cyanine compound providing a cation is exemplified by a compoundrepresented by general formula (I):

wherein ring A is a group represented by structural formula (a), (b), or(d); ring B is a group represented by structural formula (b) or (c); andQ is a polymethine linking group, the polymethine chain of which maycontain a ring structure and may have its hydrogen atom substituted witha halogen atom, a cyano group, a hydroxyl group, an alkyl group, analkoxy group, or an aryl group, these groups may be further substituted.

wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R²⁰, R²¹, R²², and R²³ eachrepresent a hydrogen atom, a hydroxyl group, a substituted orunsubstituted alkyl group having 1 to 8 carbon atoms, a substituted orunsubstituted alkoxy group having 1 to 8 carbon atoms, a substituted orunsubstituted aryl group having 6 to 30 carbon atoms, a substituted orunsubstituted aralkyl group having 7 to 30 carbon atoms, a halogen atom,a nitro group, a cyano group, or a substituent represented by generalformula (II) below; R¹ and R², R⁴ and R⁵, R⁶ and R⁷, R²⁰ and R²¹, R²¹and R²², or R²² and R²³ may be connected to each other to form acarbocyclic or heterocyclic ring having 3 to 12 carbon atoms; X¹ and X²each represent an oxygen atom, a sulfur atom, a selenium atom, —CR⁸R⁹—,—NH—, or —NY^(a)—; R⁸ and R⁹ each represent a substituted orunsubstituted alkyl group having 1 to 8 carbon atoms, a substituted orunsubstituted aryl group having 6 to 30 carbon atoms, a substituted orunsubstituted aralkyl group having 7 to 30 carbon atoms, a substituentrepresented by general formula (II) below, or a substituent representedby general formula (III) below; Y^(a), Y¹, Y², Y³, and Y⁴ each representa hydrogen atom, a substituted or unsubstituted alkyl group having 1 to8 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to8 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30carbon atoms, a substituted or unsubstituted aralkyl group having 7 to30 carbon atoms, or a substituent represented by general formula (II)below, wherein the methylene moiety of the alkyl group may besubstituted with —O— or —CO—.

wherein R^(a), R^(b), R^(c), R^(d), R^(e), R^(f), R^(g), R^(h), andR^(i) each represent a hydrogen atom, a hydroxyl group, or an alkylgroup having 1 to 4 carbon atoms, wherein the alkylene moiety of whichmay be substituted with —O— or —CO—; Z represents a direct bond or asubstituted or unsubstituted alkylene group having 1 to 8 carbon atoms,wherein the methylene moiety of which may be substituted with —O—, —S—,—CO—, —COO—, —OCO—, —SO₂—, —NH—, —CONH—, —NHCO—, —N═CH—, or —CH═CH—; andM represents a metal atom.

wherein R¹⁰, R¹¹, R¹², and R¹³ each represent a hydrogen atom, a halogenatom, a substituted or unsubstituted alkyl group having 1 to 4 carbonatoms, or a substituted or unsubstituted alkoxy group having 1 to 4carbon atoms; and R¹⁰ and R¹¹ may be connected to each other to form acarbocyclic or heterocyclic ring having 3 to 12 carbon atoms.

In general formula (I), the linking group as represented by Q, thepolymethine chain of which may contain a ring structure is preferablyexemplified by groups represented by structural formulae (1) through(10):

wherein R¹⁴, R¹⁵, R¹⁶, R¹⁷, R¹⁸, and R¹⁹ each represent a hydrogen atom,a hydroxyl group, a halogen atom, a cyano group, an aryl group having 6to 30 carbon atoms, a diphenylamino group, an alkyl group having 1 to 8carbon atoms, or an alkoxy group having 1 to 8 carbon atoms; and Z′represents a hydrogen atom, a hydroxyl group, a halogen atom, a cyanogroup, a diphenylamino group, an aryl group having 6 to 30 carbon atoms,an aralkyl group having 7 to 30 carbon atoms, or an alkyl group having 1to 8 carbon atoms, wherein the alkyl group or the alkylene moiety of thearalkyl group may be substituted with an ether linkage or a thioetherlinkage.

In general formula (I), examples of the substituted or unsubstitutedalkyl group with 1 to 8 carbon atoms as represented by R¹, R², R³, R⁴,R⁵, R⁶, R⁷, R⁸, R⁹, R²⁰, R²¹, R²², R²³, Y^(a), Y¹, Y², Y³, and Y⁴include methyl, ethyl, propyl, isopropyl, butyl, s-butyl, t-butyl,isobutyl, amyl, isoamyl, t-amyl, hexyl, cyclohexyl, cyclohexylmethyl,cyclohexylethyl, heptyl, isoheptyl, t-heptyl, n-octyl, isooctyl,t-octyl, 2-ethylhexyl, trifluoromethyl, trichloromethyl, tribromomethyl,1,2-dichloroethyl, and 3,3,3-trifluoropropyl. Examples of thesubstituted or unsubstituted alkoxy group with 1 to 8 carbon atoms asrepresented by R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R²⁰, R²¹, R²², R²³, Y^(a),Y¹, Y², Y³, and Y⁴ include methoxy, ethoxy, isopropoxy, propoxy, butoxy,pentyloxy, isopentyloxy, hexyloxy, heptyloxy, octyloxy, 2-ethylhexyloxy,trifluoromethoxy, trichloromethoxy, and tribromomethoxy. Examples of thesubstituted or unsubstituted aryl group with 6 to 30 carbon atoms asrepresented by R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R²⁰, R²¹, R²², R²³,Y^(a), Y¹, Y², Y³, and Y⁴ in general formula (I) include phenyl,naphthyl, 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 4-vinylphenyl,3-isopropylphenyl, 4-isopropylphenyl, 4-butylphenyl, 4-isobutylphenyl,4-t-butylphenyl, 4-hexylphenyl, 4-cyclohexylphenyl, 4-octylphenyl,4-(2-ethylhexyl)phenyl, 4-stearylphenyl, 2,3-dimethylphenyl,2,4-dimethylphenyl, 2,5-dimethylphenyl, 2,6-dimethylphenyl,3,4-dimethylphenyl, 3,5-dimethylphenyl, 2,4-di-t-butylphenyl,2,5-di-t-butylphenyl, 2,6-di-t-butylphenyl, 2,4-di-t-pentylphenyl,2,5-di-t-amylphenyl, 2,5-di-t-octylphenyl, 2,4-dicumylphenyl,cyclohexylphenyl, biphenyl, and 2,4,5-trimethylphenyl. Examples of thesubstituted or unsubstituted aralkyl group with 7 to 30 carbon atoms asrepresented by R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R²⁰, R²¹, R²², R²³,Y^(a), Y¹, Y², Y³ and Y⁴ include benzyl, phenethyl, 2-phenylpropan-2-yl,and diphenylmethyl, triphenylmethyl, styryl, cinnamyl. Examples of thehalogen atom as represented by R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R²⁰, R²¹,R²², and R²³ include a fluorine atom, a chlorine atom, a bromine atom,and an iodine atom. Examples of the carbocyclic or heterocyclic ringhaving 3 to 12 carbon atoms as formed by the connection of R¹ and R², R⁴and R⁵, R⁶ and R⁷, R²⁰ and R²¹, R²¹ and R²², or R²² and R²³ includearomatic rings, such as benzene, naphthalene, chlorobenzene,bromobenzene, methylbenzene, ethylbenzene, methoxybenzene, andethoxybenzene; heterocyclic rings, such as furan, benzofuran, pyrrole,thiophene, pyridine, quinoline, and thiazole; and aliphatic rings, suchas cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane,and cyclooctane. The methylene moiety of the alkyl group in Y^(a), Y¹,Y², Y³, and Y⁴ may be substituted with —O— or —CO—.

In general formula (II), examples of the alkyl group having 1 to 4carbon atoms as represented by R^(a), R^(b), R^(c), R^(d), R^(e), R^(g),R^(h), or R^(i) include methyl, ethyl, propyl, isopropyl, butyl,s-butyl, t-butyl, and isobutyl. Examples of the alkyl group with itsmethylene moiety substituted with —O— include methoxy, ethoxy, propoxy,isopropoxy, methoxymethyl, ethoxymethyl, and 2-methoxyethyl. Examples ofthe alkyl group a methylene moiety of which is substituted with —CO—include acetyl, 1-carbonylethyl, acetylmethyl, 1-carbonylpropyl,2-oxobutyl, 2-acetylethyl, and 1-carbonylisopropyl. Examples of thesubstituted or unsubstituted alkylene group having 1 to 8 carbon atomsas represented by Z include methylene, ethylene, propylene,trimethylene, tetramethylene, 1,3-butanediyl, 2-methyl-1,3-propanediyl,2-methyl-1,3-butanediyl, 2-methyl-1,4-butanediyl, pentamethylene,1,4-pentanediyl, 2,4-pentanediyl, 2-methyl-1,4-pentanediyl,hexamethylene, heptamethylene, octamethylene, ethane-1,1-diyl, andpropane-2,2-diyl. Examples of the alkylene group whose methylene moietyis substituted with —O—, —S—, —CO—, —COO—, —OCO—, —SO₂—, —NH—, —CONH—,—NHCO—, —N═CH—, or —CH═CH— include methyleneoxy, ethyleneoxy,oxymethylene, thiomethylene, carbonylmethylene, carbonyloxymethylene,methylenecarbonyloxy, sulfonylmethylene, aminomethylene, acetylamino,ethylenecarboxyamide, ethaneimidoyl, ethenylene, and propenylene.Examples of the metal atom as represented by M include Fe, Co, Ni, Ti,Cu, Zn, Zr, Cr, Mn, Os, Mn, Ru, Sn, Pd, Rb, Pt, and Ir.

In general formula (III), examples of the halogen atom, the substitutedor unsubstituted alkyl group with 1 to 4 carbon atoms, and thesubstituted or unsubstituted alkoxy group with 1 to 4 carbon atoms asrepresented by R¹⁰, R¹¹, R¹², or R¹³ and the carbocyclic or heterocyclicring with 3 to 12 carbon atoms as formed by the linkage of R¹⁰ and R¹¹are the same as those recited with respect to the corresponding groupsin general formula (I).

Of the cations of the cyanine compounds represented by general formula(I), those of compounds represented by general formula (V) below arepreferred for use in an optical filter; for they are produced at lowercost and provide a clay mineral complex having higher resistance tolight, heat, and moist heat.

wherein R¹, R², R⁶, R⁷, X¹, X², Y¹, Y³, and Q are as defined for generalformula (I).

Of the cations of the cyanine compounds represented by general formula(V), still preferred for use in an optical filter are those of compoundsrepresented by general formula (IV) below because they provide a claymineral complex with higher resistance to heat and moist heatparticularly when used in the pressure-sensitive adhesive layer of theoptical filter.

wherein Q, Y¹, Y³, X¹, and X² are as defined for general formula (I).

The following compounds (compound Nos. 1 through 49) are specificexamples of the cyanine compound of general formula (I) as a cation.

Examples of the diimmonium compound providing a cation include compoundsrepresented by general formula (VI):

wherein R³¹, R³², R³³, R³⁴, R³⁵, R³⁶, R³⁷, and R³⁸ each represent ahydrogen atom or a substituted or unsubstituted alkyl group having 1 to8 carbon atoms; R³⁹, R⁴⁰, R⁴¹, and R⁴² each represent a hydrogen atom, ahalogen atom, a substituted or unsubstituted alkyl group having 1 to 8carbon atoms, or a substituted or unsubstituted amino group, wherein themethylene moiety of the alkyl group may be substituted with —O— or—CH═CH—; and n represents an integer of to 4.

In general formula (VI), examples of the substituted or unsubstitutedalkyl group having 1 to 8 carbon atoms as represented by R³¹, R³², R³³,R³⁴, R³⁵, R³⁶, R³⁷, R³⁸, R³⁹, R⁴⁰, R⁴¹, and R⁴² and examples of thehalogen atom as represented by R³⁹, R⁴⁰, R⁴¹, and R⁴² are the same asthose recited above, e.g., for R¹, R², R³, R⁴, R⁵, R⁶, and R⁷ in generalformula (I). Examples of the substituted or unsubstituted amino group asrepresented by R³⁹, R⁴⁰, R⁴¹, and R⁴² include amino, ethylamino,dimethylamino, diethylamine, butylamino, cyclopentylamino,2-ethylhexylamino, dodecylamino, anilino, chlorophenylamino, toluidino,anisidino, N-methyl-anilino, diphenylamino, naphthylamino,2-pyridylamino, methoxycarbonylamino, phenoxycarbonylamino, acetylamino,benzoylamino, formylamino, pivaloylamino, lauroylamino, carbamoylamino,N,N-dimethylaminocarbonylamino, N,N-diethylaminocarbonylamino,morpholinocarbonylamino, methoxycarbonylamino, ethoxycarbonylamino,t-butoxycarbonylamino, n-octadecyloxycarbonylamino,N-methyl-methoxycarbonylamino, phenoxycarbonylamino, sulfamoylamino,N,N-dimethylaminosulfonylamino, methylsulfonylamino, butylsulfonylamino,and phenylsulfonylamino.

The following compounds (compound Nos. 50 through 57) are specificexamples of the diimmonium compounds represented by general formula(VI).

In the cases where a single species is used as the dye cation (C), it ispreferred to use the compound represented by general formula (IV)(hereinafter “compound (IV)”) or the compound represented by generalformula (VI) (hereinafter “compound (VI)”). When two or more species ofcations are used in combination, it is preferred, too, to use at leastone of the compound (IV) and the compound (VI). When the compound (IV)and the compound (VI) are used in combination, the mass ratio of thecompound (IV) to the compound (VI) is preferably 1:1 to 1:100, morepreferably 1:5 to 1:50.

In the case where a compound (IV) and a compound (VI) are used incombination, the clay mineral complex of the invention may be preparedby intercalating both the compound (IV) and the compound (VI) into alayered clay mineral or mixing a clay mineral intercalated with thecompound (IV) and a clay mineral intercalated with the compound (VI).

The organic cation (D) is exemplified by a quaternary ammonium ion and aphosphonium ion.

The quaternary ammonium ion preferably has an alkyl group, an arylgroup, or an aralkyl group. Particularly preferred quaternary ammoniumions are those having an alkyl group with 1 to 20 carbon atoms, thosehaving an aryl group with 6 to 30 carbon atoms, and those having anaralkyl group with 7 to 30 carbon atoms; for they have high affinitywith an organic solvent when exchanged with the dye cation (C) and havea moderate viscosity when dispersed in an organic solvent. Examples ofthe quaternary ammonium ion include tetramethylammonium ion,tetraethylammonium ion, tetra-n-decylammonium ion,tetra-n-dodecylammonium ion, trioctylmethylammonium ion,trimethylstearylammonium ion, dimethyldistearylammonium ion,trilaurylmethylammonium ion, dimethyldioctadecylammonium ion,dimethyldidecylammonium ion, dimethylstearylbenzylammonium ion, and acation of a compound represented by formula:

Examples of the phosphonium ion include an alkylphosphonium ion and anarylphosphonium ion.

wherein R²⁴, R²⁵, R²⁶, and R²⁷ each represent an alkyl group having 1 to20 carbon atoms.

The clay mineral complex (A) according to the invention is formed byintercalating the layered clay mineral (B) with the dye cation (C) andthe organic cation (D). The ratio of the dye cation (C) and the organiccation (D) to one part of the layered clay mineral (B) is preferably0.01 to 0.9 parts, more preferably 0.1 to 0.5 parts, of the dye cation(C) and 0.1 to 0.99 parts, more preferably 0.5 to 0.9 parts, of theorganic cation (D). When the ratio of the organic cation (D) is lessthan 0.1 parts, the content of the dye cation (C) is small, whichnecessitates an increase in the amount of the clay mineral complex (A)to be used. When it is more than 0.9 parts, the clay mineral complex (A)has reduced dispersibility in an organic solvent, which can result inpoor fabricability into an optical filter. When a mixture of two or morekinds of the dye cations is used as component (C), the above recitedranges of the ratios apply to the total amount of the dye cations (C).

The method of making the clay mineral complex (A) according to theinvention is not particularly limited. For example, the clay mineralcomplex (A) is obtained as follows. In the case of starting with alipophilic layered clay mineral (B) obtained by previously intercalatinga layered clay mineral (B) with an organic cation (D) forlipophilization, a suspension of the lipophilic layered clay mineral (B)in an organic solvent and a solution of a salt between a dye cation (C)and an anion in an organic solvent are mixed to exchange part of theinterlayer organic cations (D) in the lipophilic layered clay mineral(B) with the dye cation (C), and the resulting product is separated,purified, and dried to give a desired clay mineral complex (A).

In the case of starting with a hydrophilic layered clay mineral (B), theclay mineral complex (A) is obtained by (i) a method includingdispersing the layered clay mineral (B) in water to prepare asuspension, exchanging the interlayer ion of the layered clay mineralwith an organic cation (D), adding an acid until the dispersion isrendered weakly basic to acidic, and isolating and drying the resultingproduct or (ii) a method including dispersing the layered clay mineralin water, adding an acid until the dispersion is rendered weakly basicto acidic, dispersing the resulting layered clay mineral in water toprepare a suspension, exchanging the interlayer ion of the layered claymineral with an organic cation (D), and separating and drying theresulting product. Both the methods (i) and (ii) further includesexchanging part of the interlayer organic cations (D) of the driedproduct with a dye cation (C) in the same manner as with the case ofusing the lipophilic layered clay mineral (B) to obtain a desired claymineral complex (A) of the invention.

If the product as formed in the above described methods is used as aclay mineral complex without being separated and dried to prepare acoating composition for an optical filter, a component insoluble in anorganic solvent, such as a quaternary ammonium salt, remains in thecoating composition. As a result, the optical filter has reduced moistheat resistance, and ion exchange between the interlayer organic cations(D) and the dye cations (C) is hindered, raising the need to increasethe amount of the layered clay mineral (B) to be used. This leads tothickening a coating composition, flocculation of the clay mineralcomplex (A), or increasing the cost.

Examples of the binder resin (E) that can be used in the inventioninclude naturally occurring polymers, such as gelatin, casein, starch,cellulose derivatives, and alginic acid; synthetic polymers, such aspolymethyl methacrylate, polyvinyl butyral, polyvinylpyrrolidone,polyvinyl alcohol, polyvinyl chloride, styrene-butadiene copolymers,polystyrene, polyester, polyether, polycarbonate, polyamide, polyimide,polyurethane, melamine resins, and cyclic olefin resins; andpressure-sensitive adhesives.

Transparent pressure-sensitive adhesives known for laminated glass canbe used, including silicon-, urethane- or acrylic-based pressuresensitive adhesives, polyvinyl butyral pressure-sensitive adhesives,polyvinyl ether pressure sensitive adhesives, ethylene-vinyl acetatepressure sensitive adhesives, polyolefin pressure sensitive adhesives,SBR pressure sensitive adhesives, and rubber pressure sensitiveadhesives. Preferred of them are acrylic pressure sensitive adhesives,particularly acidic acrylic pressure sensitive adhesives. The pressuresensitive adhesive may be used in combination with an organic solvent, atackifier, a softener, a light resistance imparting agent, anultraviolet absorber, an antioxidant, a plasticizer, a defoaming agent,a leveling agent, a dispersant, a curing agent, and so forth.

The acrylic pressure sensitive adhesives include, but are not limitedto, a homopolymer, or a copolymer of two or more, of monomers having areactive functional group (e.g., carboxyl, hydroxyl, amido, amino orepoxy) and an ethylenically unsaturated double bond and a copolymer ofthe above described monomer having a reactive functional group and anethylenically unsaturated double bond and a monomer having anethylenically unsaturated double bond (e.g., a (meth)acrylic monomer ora vinyl monomer). If necessary, a crosslinking agent, such as a metalchelate compound, isocyanate compound, a melamine compound, an epoxycompound, an amine compound, an aziridine compound, or an oxazolinecompound, may be incorporated into the acrylic pressure sensitiveadhesive as a curing agent to improve cohesive force of the adhesive.

Commercially available acrylic pressure sensitive agents may be used,including DB Bond 5541 (from Daiabond Industry Co., Ltd.), SK DyneAS-1925, KP-2230, and SK-1811L (from Soken Chemical & Engineering Co.,Ltd.), DX2-PDP19 (from Nippon Shokubai Co., Ltd.), AT-3001 (from SaidenChemical Industry Co., Ltd.), Oribain BPS5896 (from Toyo Ink Mfg. Co.,Ltd.), and CS-9611 (from Nitto Denko Corp.).

The amounts of the clay mineral complex (A) and the binder resin (E) inthe optical filter of the invention are not particularly limited but aregenerally as follows. In making an optical filter having a pressuresensitive adhesive layer, for example, a pressure sensitive adhesivesolution is prepared from 100 parts by mass of a pressure sensitiveadhesive (as the binder resin (E)), 0.0001 to 50 parts, preferably 0.001to 5.0 parts, by mass of the layered clay mineral complex (A), and 0.1to 1000 parts, preferably 1.0 to 500 parts, by mass of a solvent (e.g.,methyl ethyl ketone). The pressure sensitive adhesive solution isapplied to a transparent substrate, such as a PET film having beensubjected to an adhesion enhancing treatment, and dried to provide anoptical filter with a pressure sensitive adhesive layer having athickness of 2 to 400 μm, preferably 5 to 40 μm. In the case of makingan optical filter containing the essential components (A) to (C) andoptional components, the same ratios of the components as describedabove shall apply.

In the case where the clay mineral complex (A), the binder resin (E),and optional components, such as a light absorber and variousstabilizers, are incorporated into a pressure sensitive adhesive layerbetween adjacent two members selected from the transparent substrate andany optional layers, the two members selected from the transparentsubstrate and the optional layers are bonded together using a pressuresensitive adhesive containing the clay mineral complex (A) and others. Aknown separator film, such as a polyethylene terephthalate film havingbeen subjected to an adhesion enhancing treatment, may be provided onthe surface of the pressure sensitive adhesive layer.

The optical filter of the invention is useful in applications to imagedisplays, such as liquid crystal displays (LCDs), plasma display panels(PDPs), electroluminescence displays (ELDs), cathode ray tubes (CRTs),CCD image sensors, CMOS sensors, vacuum fluorescent displays, and fieldemission displays; analysis equipment, fabrication of semiconductordevices, astronomical observation, optical communications, spectaclelenses, windows, and so on.

When applied to an image display, the optical filter of the invention isusually disposed in front of a display device. The optical filter may beaffixed directly to the front surface of a display device or to thefront or the back side of a front plate or an electromagnetic shield ifprovided in front of a display device.

When applied to an image display, the optical filter of the inventionmay contain a light absorber that absorbs light of wavelengths except480 to 500 nm to adjust the color tone or a light absorber that absorbslight of wavelengths of 480 to 500 nm other than the salt of the dyecation and an anion used in the invention in order to prevent reflectionof ambient light or image light. When applied to a plasma display, theoptical filter may contain a near infrared absorber that absorbs lightof 750 to 1100 nm other than the salt of the dye cation and an anion ofthe invention.

The light absorber for color tone adjustment is exemplified by thoseused to remove orange light of 550 to 600 nm, which include trimethinecyanine derivatives, such as trimethine indolium compounds, trimethinebenzoxazolium compounds, and trimethine benzothiazolium compounds;pentamethine cyanine derivatives, such as pentamethine oxazoliumcompounds and pentamethine thiazolium compounds; squarylium dyederivatives, azomethine dye derivatives, xanthene dye derivatives, azodye derivatives, pyrromethene derivatives, azo metal complexderivatives, rhodamine dye derivatives, phthalocyanine derivatives,porphyrin derivatives, and dipyrromethene metal chelate compounds.

Examples of the light absorber that absorbs light of 480 to 500 nm forpreventing reflection of ambient light include monomethine cyaninederivatives; trimethine cyanine derivatives, such as trimethine indoliumcompounds, trimethine oxazolium compounds, trimethine thiazoliumcompounds, and indolidene trimethine thiazonium compounds; merocyaninederivatives, phthalocyanine derivatives, naphthalocyanine derivatives,porphyrin derivatives, and dipyrromethene metal chelate compounds.

Examples of the near infrared absorber that absorbs light of 750 to 1100nm to prevent malfunction of an infrared remote controller includepentamethine cyanine derivatives, such as pentamethine benzoindoliumcompounds, pentamethine benzoxazolium compounds, and pentamethinebenzothiazolium compounds; heptamethine cyanine derivatives, such asheptamethine indolium compounds, heptamethine benzoindolium compounds,heptamethine oxazolium compounds, heptamethine benzoxazolium compounds,heptamethine thiazolium compounds, and heptamethine benzothiazoliumcompounds; diimmonium compounds, aminium compounds, squaryliumderivatives; nickel complexes, such as bis(stilbenedithiolato)compounds, bis(benzenedithiolato)nickel compounds, andbis(camphordithiolato)nickel compounds; azo dye derivatives,phthalocyanine derivatives, porphyrin derivatives, and dipyrromethenemetal chelate compounds.

The optical filter of the invention may contain the light absorber forcolor tone adjustment, the light absorber for absorbing light of 480 to500 nm, and the infrared absorber in the same layer that contains theclay mineral complex (A) or any other layer. They are each used in anamount of 10 to 5000 parts by mass per 100 parts by mass of the claymineral complex (A).

A typical structure of the optical filter of the present inventionincludes a transparent substrate, on which a primer layer, anantireflective layer, a hard coat layer, a lubricating layer, a pressuresensitive adhesive layer, or a like layer is disposed as needed. Whilethe method of incorporating the clay mineral complex (A), the binderresin (E), and optional components, such as a light absorber and variousstabilizers, into the optical filter is not particularly restricted, itis preferred that these components be incorporated in a pressuresensitive adhesive layer between any two adjacent members selected fromthe transparent substrate and the optional layers.

The transparent substrate can be of inorganic materials, such as glass,and polymeric materials. Examples of polymeric materials includecellulose esters, such as diacetyl cellulose, triacetyl cellulose (TAC),propionyl cellulose, butyryl cellulose, acetylpropionyl cellulose, andnitrocellulose; polyamides; polyimides; polyurethanes; epoxy resins;polycarbonates; polyesters, such as polyethylene terephthalate,polyethylene naphthalate, polybutylene terephthalate,poly(1,4-cyclohexane dimethylene terephthalate),poly(ethylene-1,2-diphenoxyethane-4,4′-dicarboxylate), and polystyrenes;polyolefins, such as polyethylene, polypropylene, and polymethylpentene;vinyl compounds, such as polyvinyl acetate, polyvinyl chloride, andpolyvinyl fluoride; acrylic resins, such as polymethyl methacrylate andpolyacrylic esters; polysulfones; polyether sulfones; polyether ketones;polyether imides; polyoxyethylenes; and norbornene resins. It ispreferred for the transparent substrate to have a transmittance of atleast 80%, still preferably 86% or higher; a haze of not more than 2%,still preferably 1% or less; and a refractive index of 1.45 to 1.70.

The transparent substrate may contain an infrared absorber, anultraviolet absorber, an antioxidants (e.g., a phenolic orphosphorous-containing antioxidant), a flame retardant, a lubricant, anantistatic agent, inorganic One particles, and the like. The transparentsubstrate may be subjected to various surface treatments.

Examples of the inorganic fine particles include silicon dioxide,titanium dioxide, barium sulfate, and calcium carbonate.

The surface treatments include chemical treatments, mechanicaltreatments, a corona discharge treatment, a flame treatment, a UVirradiation treatment, a radiofrequency treatment, a glow dischargetreatment, an active plasma treatment, a laser treatment, a mixed acidtreatment, and an ozone oxidation treatment.

The primer layer is a layer provided between the transparent substrateand a light absorbing layer containing a light absorber if provided. Theprimer layer is a layer containing a polymer having a glass transitiontemperature of −60° to 60° C., a layer with a rough surface on the lightabsorbing layer side thereof, or a layer containing a polymer havingaffinity to the polymer of the light absorbing layer. Even where anindependent light absorbing layer is not provided, a primer layer may beprovided on the transparent substrate to improve the adhesion betweenthe substrate and a layer provided thereon (e.g., an antireflectivelayer or a hard coat layer). A primer layer may also be provided inorder to improve the affinity of the optical filter to an adhesive withwhich the optical filter is to be affixed to an image display device.

The thickness of the primer layer is suitably 2 nm to 20 μm, preferably5 nm to 5 μm, more preferably 20 nm to 2 μm, even more preferably 50 nmto 1 μm, most preferably 80 nm to 300 nm. The primer layer containing apolymer whose glass transition temperature ranges from −60° to 60° C.serves to bond the transparent substrate and a filter layer because ofits tackiness. Examples of the polymer whose glass transitiontemperature is −60° to 60° C. include homo- and copolymers of vinylchloride, vinylidene chloride, vinyl acetate, butadiene, neoprene,styrene, chloroprene, acrylic esters, methacrylic esters, acrylonitrileor methyl vinyl ether. The glass transition temperature of the polymeris preferably 50° C. or lower, more preferably 40° C. or lower, evenmore preferably 30° C. or lower, still even more preferably 25° C. orlower, most preferably 20° C. or lower. It is preferred for the primerlayer to have an elastic modulus of 1 to 1000 MPa, more preferably 5 to800 MPa, even more preferably 10 to 500 MPa, at 25° C.

The primer layer with a rough surface serves for adhesion between thetransparent substrate and a light absorbing layer provided on the roughsurface side thereof. Such a primer layer can easily be formed byapplying a polymer latex. The polymer latex preferably has an averageparticle size of 0.02 to 3 μm, more preferably 0.05 to 1 μm.

Examples of the polymer having affinity to the polymer (binder) of thelight absorbing layer include acrylic resins, cellulose derivatives,gelatin, casein, starch, polyvinyl alcohol, soluble nylon, and polymerlatices.

The optical filter may have two or more primer layers. The primer layermay contain a solvent for swelling a transparent substrate, a mattingagent, a surfactant, an antistatic agent, a coating aid, a hardener, andso forth.

The antireflective layer essentially contains a low refractive sublayerhaving a lower refractive index than the transparent substrate. Therefractive index of the low refractive sublayer is preferably 1.20 to1.55, still preferably 1.30 to 1.50. The thickness of the low refractivesublayer is preferably 50 to 400 nm, still preferably 50 to 200 nm. Thelow refractive sublayer may be a layer of low-refractive,fluorine-containing polymer (see JP 57-34526A, JP 3-130103A, JP6-115023A, JP 8-313702A, and JP 7-168004A), a layer formed by a sol-gelprocess (see JP 5-208811A, JP 6-299091A, and JP 7-168003A), or a layercontaining fine particles (see JP 60-59250B, JP 5-13021A, JP 6-56478A,JP 7-92306A, and JP 9-288201A). The low refractive sublayer containingfine particles has microvoids formed between the fine particles orinside the fine particles. The low refractive sublayer containing fineparticles preferably has a void of 3% to 50% by volume, still preferably5% to 35% by volume.

In order to prevent reflection over a broad wavelength range, theantireflective layer preferably contains a medium and a high refractivesublayer in addition to the low refractive sublayer. The refractiveindex of a high refractive sublayer is preferably 1.65 to 2.40, stillpreferably 1.70 to 2.20. The refractive index of a medium refractivesublayer is set to be the intermediate between the refractive indices ofthe low and the high refractive sublayers and is preferably 1.50 to1.90, still preferably 1.55 to 1.70. The thickness of the medium and thehigh refractive sublayers is preferably 5 nm to 100 μm, still preferably10 nm to 10 μm, even still preferably 30 nm to 1 μm. The haze of themedium and the high refractive sublayers is preferably 5% or less, stillpreferably 3% or less, even still preferably 1% or less. The medium andthe high refractive sublayers are formed by using polymer binders havingrelatively high refractive indices, such as polystyrene, styrenecopolymers, polycarbonates, melamine resins, acrylic resins, phenolresins, epoxy resins, and polyurethanes obtained by the reaction betweenacyclic (alicyclic or aromatic) isocyanate and a polyol. Polymers havinga cyclic (aromatic, heterocyclic or alicyclic) group and polymers havinga halogen atom except fluorine as a substituent also have highrefractive indices. Polymers prepared from monomers having a double bondintroduced therein and thereby capable of radical polymerization arealso useful.

Fine inorganic particles may be dispersed in the above recited polymerbinders to increase the refractive index. Fine inorganic particleshaving a refractive index of 1.80 to 2.80 are used preferably. Such Oneinorganic particles are preferably prepared from metal oxides orsulfides, such as titanium oxide (including rutile, rutile/anatase mixedcrystals, anatase, and amorphous oxide), tin oxide, indium oxide, zincoxide, zirconium oxide, and zinc sulfide. Preferred of them are titaniumoxide, tin oxide, and indium oxide. The fine inorganic particles maycontain the metal oxide or sulfide as a major component and otherelements as a minor component. The term “major component” means acomponent present in the particles in the highest weight proportion.Other elements that may be present include Ti, Zr, Sn, Sb, Cu, Fe, Mn,Pb, Cd, As, Cr, Hg, Zn, Al, Mg, Si, P, and S. The medium or highrefractive sublayer can also be formed by using inorganic materials thatare liquid per se or dispersible in a solvent and are capable of forminga film, such as alkoxides of various elements, salts of organic acids,coordination compounds having a coordinating compound bonded (e.g.,chelate compounds), and inorganic active polymers.

The surface of the antireflective layer may be endowed with an antiglarefunction for scattering incident light thereby preventing thesurrounding environment from reflecting on the antireflective layer. Forexample, fine roughness is formed on a transparent film, and anantireflective layer is formed on the roughened surface, or the surfaceof an antireflective layer is embossed with an embossing roll to havefine surface roughness. An antireflective layer with an antiglarefunction usually has a haze of 3% to 30%.

The hard coat layer has higher hardness than the transparent substrate.The hard coat layer preferably contains a crosslinked polymer. The hardcoat layer can be formed by using acrylic, urethane or epoxy polymers,oligomers or monomers, such as UV curing resins. The hard coat layer canalso be made of a silica-based material.

A lubricating layer may be provided on the antireflective layer (lowrefractive sublayer). A lubricating layer imparts slip properties to thesurface of the low refractive sublayer thereby improving scratchresistance. The lubricating layer can be formed usingorganopolysiloxanes (e.g., silicone oil), natural waxes, petroleumwaxes, higher fatty acid metal salts, or fluorine-containing lubricantsor derivatives thereof. The lubricating layer preferably has a thicknessof 2 to 20 nm.

Examples of the organic solvents include alcohols, such as isopropylalcohol; ether alcohols, such as methyl cellosolve, ethyl cellosolve,butyl cellosolve, and butyl diglycol; ketones, such as acetone, methylethyl ketone, methyl isobutyl ketone, cyclohexanone, and diacetonealcohol; esters, such as ethyl acetate, butyl acetate, and methoxyethylacetate; acrylic esters, such as ethyl acrylate and butyl acrylate;fluoroalcohols, such as 2,2,3,3-tetrafluoropropanol; hydrocarbons, suchas hexane, benzene, toluene, and xylene; and chlorinated hydrocarbons,such as methylene dichloride, dichloroethane, and chloroform. Theseorganic solvents may be used either individually or as a mixturethereof.

The primer layer, antireflective layer, hard coat layer, lubricatinglayer, light absorbing layer, pressure sensitive adhesive layer, and thelike can be formed by commonly employed coating methods including dipcoating, air knife coating, curtain coating, roller coating, wire barcoating, gravure coating, and extrusion coating using a hopper (see U.S.Pat. No. 2,681,294). Two or more layers can be formed by simultaneouscoating. For the details of simultaneous coating techniques, referencecan be made in U.S. Pat. Nos. 2,761,791, 2,941,898, 3,508,947, and3,526,528, and Harasaki Yuji, Coating Kogaku, Asakura Shoten, 1973, 253.

EXAMPLES

The present invention will now be illustrated in greater detail withreference to Evaluation Examples, Comparative Evaluation Examples, andExamples, but it should be understood that the invention is notconstrued as being limited thereto. Preparation Examples 1 to 4 showexamples of synthesis of the clay mineral complexes according to theinvention. Evaluation Examples 1 to 4 show evaluation of durability ofthe clay mineral complex according to the invention. Examples 1 to 3demonstrate fabrication of the optical filter containing the claymineral complex of the invention.

Preparation Example 1 Synthesis of Clay Mineral Complex 1

A dispersion (20 g) of 1.0 g of Lucentite SAN210-A (lipophilic smectite,from CO—OP Chemical Co., Ltd.) as a layered clay mineral (B) in 19 g ofmethyl ethyl ketone and a solution (6 g) of 0.3 g of abistrifluoromethylsulfonylimide salt of compound No. 1 as a dye cation(C) in 5.7 g of methyl ethyl ketone were mixed and stirred for 1 hour toexchange part of the interlayer organic cation (D) of Lucentite SAN210-Awith compound No. 1 (dye cation (C)). To the reaction system was added150 ml of methanol. The solid thus precipitated was collected byfiltration and washed successively with water and methanol to give 0.75g of clay mineral complex 1.

Preparation Example 2 Synthesis of Clay Mineral Complex 2

Clay mineral complex 2 weighing 0.64 g was obtained in the same manneras in Preparation Example 1, except for using a solution (6 g) having0.5 g of compound No. 1 bistrifluoromethylsulfonylimide salt dissolvedin 5.5 g of methyl ethyl ketone.

Preparation Example 3 Synthesis of Clay Mineral Complex 3

A dispersion (20 g) of 1.0 g of Lucentite SAN210-A (lipophilic smectite,from CO—OP Chemical Co., Ltd.) as a layered clay mineral (B) in 19 g ofmethyl ethyl ketone and a solution (6 g) of 0.3 g of abistrifluoromethylsulfonylimide salt of compound No. 50 (dye cation (C))in 5.7 g of methyl ethyl ketone were mixed and stirred for 1 hour. Tothe reaction system was added 150 ml of methanol. The solid thusprecipitated was collected by filtration and washed successively withwater and methanol to give 0.77 g of clay mineral complex 3.

Preparation Example 4 Synthesis of Clay Mineral Complex 4

Clay mineral complex 4 weighing 0.58 g was obtained in the same manneras in Preparation Example 1, except for using 6 g of a solution having0.5 g of compound No. 50 bistrifluoromethylsulfonylimide salt dissolvedin 5.5 g of methyl ethyl ketone.

Confirmation of Intercalation

In order to confirm the presence of the dye cation intercalated in theclay mineral complexes obtained in Preparation Examples 1 to 4, thebasal spacing of the clay mineral complex was calculated from the X-raydiffraction pattern measured with RINT2000-ULTIMA+ (from Rigaku Corp.).The results obtained are shown in Table 1. The results show an increaseof basal spacing over SAN210-A, indicating intercalation of the dyecation into the layered clay mineral.

TABLE 1 Sample Basal Spacing (A) SAN210-A 17.0 Clay mineral complex 119.5 Clay mineral complex 2 22.0 Clay mineral complex 3 19.2 Claymineral complex 4 19.2

Evaluation Examples 1 to 4 and Comparative Evaluation Examples 1 to 4Evaluation of Durability

A pressure sensitive adhesive solution prepared in accordance with theformulation below was applied to a 188 μm thick polyethyleneterephthalate (PET) film having been subjected to an adhesion enhancingtreatment by means of a bar coater #90 and dried at 100° C. for 5minutes. A 0.9 mm thick glass sheet was stuck to the PET film via theadhesive layer to make specimens. The following tests for evaluatingdurability were carried out using the specimens.

Light Resistance

The transmittance of the specimen was measured at the λ_(max) in the UVabsorption spectrum. The specimen was then irradiated with 55000 luxlight for 300 hours and 500 hours. The transmittance at the λ_(max) inthe UV absorption spectrum was again measured. The percentage of thetransmittance after the irradiation to the transmittance before theirradiation was calculated as a measure of light resistance. The resultsobtained are shown in Tables 2 and 3.

Heat Resistance

The transmittance of the specimen was measured at λ_(max) in the UVabsorption spectrum was measured. The transmittance at λ_(max) was againmeasured after the specimen was left to stand in a constant-temperaturechamber set at 80° C. for 300 hours and 500 hours. The percentage of thetransmittance after the heating to the transmittance before the heatingwas calculated as a measure of heat resistance. The results are shown inTables 2 and 3.

Moist Heat Resistance

The transmittance of the specimen was measured at λ_(max) in the UVabsorption spectrum before and after the specimen was left to stand in aconstant-temperature, constant-humidity chamber set at 60° C./90% RH for300 hours and 500 hours. The percentage of the transmittance after themoist heating to the transmittance before the moist heating wascalculated as a measure of moist heat resistance. The results are shownin Tables 2 and 3.

Formulation of Evaluation Example 1:

Clay mineral complex 1 8.00 mg Acrylic pressure sensitive adhesive 4.68g (DB Bond 5541, from Diabond Industry Co., Ltd.) Methyl ethyl ketone1.99 g

Formulation of Evaluation Example 2:

Clay mineral complex 2 6.00 mg Acrylic pressure sensitive adhesive (DBBond 5541, 4.68 g from Diabond) Methyl ethyl ketone 1.99 g

Formulation of Comparative Evaluation Example 1:

Compound No. 1 bistrifluoromethylsulfonylimide salt 2.00 mg Acrylicpressure sensitive adhesive (DB Bond 5541, 4.68 g from Diabond) Methylethyl ketone 1.99 g

Formulation of Comparative Evaluation Example 2:

Lucentite SAN210-A 4.00 mg Compound No. 1 perchlorate salt 2.00 mgAcrylic pressure sensitive adhesive (DB Bond 5541, 4.68 g from Diabond)Methyl ethyl ketone 1.99 g

TABLE 2 Light Heat Moist Heat Resistance (%) Resistance (%) Resistance(%) 300 hrs 500 hrs 300 hrs 500 hrs 300 hrs 500 hrs Evaluation 82.6 75.292.0 89.0 98.0 97.8 Example 1 Evaluation 78.8 71.8 85.6 82.3 96.4 94.3Example 2 Compara. 47.4 39.6 27.8 25.2 52.4 34.1 Evaluation Example 1Compara. 68.7 51.1 82.8 73.3 90.0 81.1 Evaluation Example 2

Formulation of Evaluation Example 3:

Clay mineral complex 3 120.00 mg Acrylic pressure sensitive adhesive (DBBond 5541,  4.68 g from Diabond) Methyl ethyl ketone  1.99 g

Formulation of Evaluation Example 4:

Clay mineral complex 4 90.00 mg Acrylic pressure sensitive adhesive (DBBond 5541,  4.68 g from Diabond) Methyl ethyl ketone  1.99 g

Formulation of Comparative Evaluation Example 3:

Compound No. 50 bistrifluoromethylsulfonylimide salt 30.00 mg Acrylicpressure sensitive adhesive (DB Bond 5541, from  4.68 g Diabond) Methylethyl ketone  1.99 g

Formulation of Comparative Evaluation Example 4:

Lucentite SAN210-A 90.00 mg Compound No. 50bistrifluoromethylsulfonylimide salt 30.00 mg Acrylic pressure sensitiveadhesive (DB Bond 5541, from  4.68 g Diabond) Methyl ethyl ketone  1.99g

TABLE 3 Light Heat Moist Heat Resistance (%) Resistance (%) Resistance(%) 300 hrs 500 hrs 300 hrs 500 hrs 300 hrs 500 hrs Evaluation 99.9 99.999.8 99.8 99.9 99.8 Example 3 Evaluation 99.7 99.0 97.1 96.1 99.5 99.2Example 4 Compara. 96.9 91.6 36.6 24.0 39.2 28.5 Evaluation Example 3Compara. 99.7 99.6 96.6 94.2 98.1 97.1 Evaluation Example 4

Example 1 Fabrication of Optical Filter 1

A pressure sensitive adhesive solution prepared according to thefollowing formulation was applied to a 188 μm thick PET film having beensubjected to an adhesion enhancing treatment using a bar coater #90 anddried at 100° C. for 10 minutes to make an optical filter having apressure sensitive adhesive layer with a thickness of about 10 μm on thePET film. The optical filter had a λ_(max), of 592 nm with a half bandwidth of 43 nm as measured with an UV-visible-near IR spectrophotometerV-570 (JASCO Corp.).

Formulation:

Clay mineral complex 1 0.12 g   Acrylic pressure sensitive adhesive (DBBond 5541, 70 g from Diabond) Methyl ethyl ketone 30 g

Example 2 Fabrication of Optical Filter 2

Optical filter 2 was fabricated in the same manner as in Example 1,except for replacing DB Bond 5541 with DX2-PDP-19 (from Nippon ShokubaiCo., Ltd.) as an acrylic pressure sensitive adhesive and additionallyusing Coronate L-55E (from Nippon Polyurethane Industry Co., Ltd.) as acuring agent. The resulting optical filter had a λ_(max) of 592 nm witha half band width of 43 nm as measured with an UV-visible-near IRspectrophotometer V-570 PASCO Corp.).

Example 3 Fabrication of Optical Filter 3

Optical filter 3 was fabricated in the same manner as in Example 1,except for using 0.09 g of clay mineral complex 2 as a clay mineralcomplex. The resulting optical filter had a λ_(max) of 592 nm with ahalf band width of 43 nm as measured with an UV-visible-near IRspectrophotometer V-570 (JASCO Corp.).

Evaluation Examples, Comparative Evaluation Examples, and Examples GivenAbove Reveal the Following Facts.

In systems having a pressure sensitive adhesive according to theinvention, the optical filters of Evaluation Examples 1 to 4 whichcontain the clay mineral complex of the invention are superior inresistance to 300-hour and 500-hour exposure to light, heat, and moistheat to those of Comparative Evaluation Examples 1 and 3 which contain asalt of a dye cation and an anion in place of the clay mineral complexand those of Comparative Evaluation Examples 2 and 4 which contain amixture of a layered clay mineral and a salt of a dye cation and ananion in place of the clay mineral complex. It has now been proved thatthe optical filter of the present invention that contains the claymineral complex of the invention and the pressure sensitive adhesive ofthe invention exhibits light resistance withstanding practical use andis particularly superior in heat resistance and moist heat resistance.

INDUSTRIAL APPLICABILITY

The optical filter of the present invention is superior in lightresistance and moist heat resistance. The optical filter is suitable toimprove display quality of image displays and to prevent reflection ofambient light.

1-11. (canceled)
 12. An optical filter comprising at least a claymineral complex (A), the clay mineral complex (A) comprising a layeredclay mineral (B) intercalated with a dye cation (C) and an organiccation (D).
 13. The optical filter according to claim 12, furthercomprising a binder resin (E).
 14. The optical filter according to claim12, wherein the layered clay mineral (B) is smectite.
 15. The opticalfilter according to claim 12, wherein the dye cation (C) is a cation ofa cyanine compound represented by general formula (I):

wherein ring A is a group represented by structural formula (a), (b), or(d); ring B is a group represented by structural formula (b) or (c); andQ is a polymethine linking group, the polymethine chain of which maycontain a ring structure and may have its hydrogen atom substituted witha halogen atom, a cyano group, a hydroxyl group, an alkyl group, analkoxy group, or an aryl group, these groups may be further substituted,

wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R²⁰, R²¹, R²², and R²³ eachrepresent a hydrogen atom, a hydroxyl group, a substituted orunsubstituted alkyl group having 1 to 8 carbon atoms, a substituted orunsubstituted alkoxy group having 1 to 8 carbon atoms, a substituted orunsubstituted aryl group having 6 to 30 carbon atoms, a substituted orunsubstituted aralkyl group having 7 to 30 carbon atoms, a halogen atom,a nitro group, a cyano group, or a substituent represented by generalformula (II) below; R¹ and R², R⁴ and R⁵, R⁶ and R⁷, R²⁰ and R²¹, R²¹and R²², or R²² and R²³ may be connected to each other to form acarbocyclic or heterocyclic ring having 3 to 12 carbon atoms; X¹ and X²each represent an oxygen atom, a sulfur atom, a selenium atom, —CR⁸R⁹—,—NH—, or —NY^(a)—; R⁸ and R⁹ each represent a substituted orunsubstituted alkyl group having 1 to 8 carbon atoms, a substituted orunsubstituted aryl group having 6 to 30 carbon atoms, a substituted orunsubstituted aralkyl group having 7 to 30 carbon atoms, a substituentrepresented by general formula (II) below, or a substituent representedby general formula (III) below; Y^(a), Y¹, Y², Y³, and Y⁴ each representa hydrogen atom, a substituted or unsubstituted alkyl group having 1 to8 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to8 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30carbon atoms, a substituted or unsubstituted aralkyl group having 7 to30 carbon atoms, or a substituent represented by general formula (II)below, wherein the methylene moiety of the alkyl group may besubstituted with —O— or —CO—.

wherein R^(a), R^(b), R^(c), R^(d), R^(e), R^(f), R^(g), R^(h), andR^(i) each represent a hydrogen atom, a hydroxyl group, or an alkylgroup having 1 to 4 carbon atoms, wherein the alkylene moiety of whichmay be substituted with —O— or —CO—; Z represents a direct bond or asubstituted or unsubstituted alkylene group having 1 to 8 carbon atoms,wherein the methylene moiety of which may be substituted with —O—, —S—,—CO—, —COO—, —OCO—, —SO₂—, —NH—, —CONH—, —NHCO—, —N═CH—, or —CH═CH—; andM represents a metal atom.

wherein R¹⁰, R¹¹, R¹², and R¹³ each represent a hydrogen atom, a halogenatom, a substituted or unsubstituted alkyl group having 1 to 4 carbonatoms, or a substituted or unsubstituted alkoxy group having 1 to 4carbon atoms; and R¹⁰ and R¹¹ may be connected to each other to form acarbocyclic or heterocyclic ring having 3 to 12 carbon atoms.
 16. Theoptical filter according to claim 15, wherein the cation of the cyaninecompound is represented by general formula (IV):

wherein Q, Y¹, Y³, X¹, and X² are as defined for general formula (I).17. The optical filter according to claim 12, wherein the dye cation (C)is a cation of a diimmonium compound represented by general formula(VI):

wherein R³¹, R³², R³³, R³⁴, R³⁵, R³⁶, R³⁷, and R³⁸ each represent ahydrogen atom or a substituted or unsubstituted alkyl group having 1 to8 carbon atoms; R³⁹, R⁴⁰, R⁴¹, and R⁴² each represent a hydrogen atom, ahalogen atom, a substituted or unsubstituted alkyl group having 1 to 8carbon atoms, or a substituted or unsubstituted amino group, wherein themethylene moiety of the alkyl group may be substituted with —O— or—CH═CH—; and n represents an integer of 1 to
 4. 18. The optical filteraccording to claim 14, wherein the smectite is lipophilic smectite. 19.The optical filter according to claim 13, wherein the binder resin (E)is an acrylic pressure sensitive adhesive.
 20. The optical filteraccording to claim 19, wherein the optical filter has a pressuresensitive adhesive layer, and the clay mineral complex (A) and theacrylic pressure sensitive adhesive are present in the pressuresensitive adhesive layer.
 21. The optical filter according to claim 12,which is for application to an image display.
 22. The optical filteraccording to claim 21, wherein the image display is a plasma display.23. The optical filter according to claim 13, wherein the layered claymineral (B) is smectite.
 24. The optical filter according to claim 13,wherein the dye cation (C) is a cation of a cyanine compound representedby general formula (I):

wherein ring A is a group represented by structural formula (a), (b), or(d); ring B is a group represented by structural formula (b) or (c); andQ is a polymethine linking group, the polymethine chain of which maycontain a ring structure and may have its hydrogen atom substituted witha halogen atom, a cyano group, a hydroxyl group, an alkyl group, analkoxy group, or an aryl group, these groups may be further substituted,

wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R²⁰, R²¹, R²², and R²³ eachrepresent a hydrogen atom, a hydroxyl group, a substituted orunsubstituted alkyl group having 1 to 8 carbon atoms, a substituted orunsubstituted alkoxy group having 1 to 8 carbon atoms, a substituted orunsubstituted aryl group having 6 to 30 carbon atoms, a substituted orunsubstituted aralkyl group having 7 to 30 carbon atoms, a halogen atom,a nitro group, a cyano group, or a substituent represented by generalformula (II) below; R¹ and R², R⁴ and R⁵, R⁶ and R⁷, R²⁰ and R²¹, R²¹and R²², or R²² and R²³ may be connected to each other to form acarbocyclic or heterocyclic ring having 3 to 12 carbon atoms; X¹ and X²each represent an oxygen atom, a sulfur atom, a selenium atom, —CR⁸R⁹—,—NH—, or —NY^(a)—; R⁸ and R⁹ each represent a substituted orunsubstituted alkyl group having 1 to 8 carbon atoms, a substituted orunsubstituted aryl group having 6 to 30 carbon atoms, a substituted orunsubstituted aralkyl group having 7 to 30 carbon atoms, a substituentrepresented by general formula (II) below, or a substituent representedby general formula (III) below; Y^(a), Y¹, Y², Y³, and Y⁴ each representa hydrogen atom, a substituted or unsubstituted alkyl group having 1 to8 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to8 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30carbon atoms, a substituted or unsubstituted aralkyl group having 7 to30 carbon atoms, or a substituent represented by general formula (II)below, wherein the methylene moiety of the alkyl group may besubstituted with —O— or —CO—.

wherein R^(a), R^(b), R^(c), R^(d), R^(e), R^(f), R^(g), R^(h), andR^(i) each represent a hydrogen atom, a hydroxyl group, or an alkylgroup having 1 to 4 carbon atoms, wherein the alkylene moiety of whichmay be substituted with —O— or —CO—; Z represents a direct bond or asubstituted or unsubstituted alkylene group having 1 to 8 carbon atoms,wherein the methylene moiety of which may be substituted with —O—, —S—,—CO—, —COO—, —OCO—, —SO₂—, —NH—, CONH—, —NHCO—, —N═CH—, or —CH═CH—; andM represents a metal atom.

wherein R¹⁰, R¹¹, R¹², and R¹³ each represent a hydrogen atom, a halogenatom, a substituted or unsubstituted alkyl group having 1 to 4 carbonatoms, or a substituted or unsubstituted alkoxy group having 1 to 4carbon atoms; and R¹⁰ and R¹¹ may be connected to each other to form acarbocyclic or heterocyclic ring having 3 to 12 carbon atoms.
 25. Theoptical filter according to claim 14, wherein the dye cation (C) is acation of a cyanine compound represented by general formula (I):

wherein ring A is a group represented by structural formula (a), (b), or(d); ring B is a group represented by structural formula (b) or (c); andQ is a polymethine linking group, the polymethine chain of which maycontain a ring structure and may have its hydrogen atom substituted witha halogen atom, a cyano group, a hydroxyl group, an alkyl group, analkoxy group, or an aryl group, these groups may be further substituted,

wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R²⁰, R²¹, R²², and R²³ eachrepresent a hydrogen atom, a hydroxyl group, a substituted orunsubstituted alkyl group having 1 to 8 carbon atoms, a substituted orunsubstituted alkoxy group having 1 to 8 carbon atoms, a substituted orunsubstituted aryl group having 6 to 30 carbon atoms, a substituted orunsubstituted aralkyl group having 7 to 30 carbon atoms, a halogen atom,a nitro group, a cyano group, or a substituent represented by generalformula (II) below; R¹ and R², R⁴ and R⁵, R⁶ and R⁷, R²⁰ and R²¹, R²¹and R²², or R²² and R²³ may be connected to each other to form acarbocyclic or heterocyclic ring having 3 to 12 carbon atoms; X¹ and X²each represent an oxygen atom, a sulfur atom, a selenium atom, —CR⁸R⁹—,—NH—, or —NY^(a)—; R⁸ and R⁹ each represent a substituted orunsubstituted alkyl group having 1 to 8 carbon atoms, a substituted orunsubstituted aryl group having 6 to 30 carbon atoms, a substituted orunsubstituted aralkyl group having 7 to 30 carbon atoms, a substituentrepresented by general formula (II) below, or a substituent representedby general formula (III) below; Y^(a), Y¹, Y², Y³, and Y⁴ each representa hydrogen atom, a substituted or unsubstituted alkyl group having 1 to8 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to8 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30carbon atoms, a substituted or unsubstituted aralkyl group having 7 to30 carbon atoms, or a substituent represented by general formula (II)below, wherein the methylene moiety of the alkyl group may besubstituted with —O— or —CO—.

wherein R^(a), R^(b), R^(c), R^(d), R^(e), R^(f), R^(g), R^(h), andR^(i) each represent a hydrogen atom, a hydroxyl group, or an alkylgroup having 1 to 4 carbon atoms, wherein the alkylene moiety of whichmay be substituted with —O— or —CO—; Z represents a direct bond or asubstituted or unsubstituted alkylene group having 1 to 8 carbon atoms,wherein the methylene moiety of which may be substituted with —O—, —S—,—CO—, —COO—, —OCO—, —SO₂—, —NH—, —CONH—, —NHCO—, —N═CH—, or —CH═CH—; andM represents a metal atom.

wherein R¹⁰, R¹¹, R¹², and R¹³ each represent a hydrogen atom, a halogenatom, a substituted or unsubstituted alkyl group having 1 to 4 carbonatoms, or a substituted or unsubstituted alkoxy group having 1 to 4carbon atoms; and R¹⁰ and R¹¹ may be connected to each other to form acarbocyclic or heterocyclic ring having 3 to 12 carbon atoms.
 26. Theoptical filter according to claim 13, wherein the dye cation (C) is acation of a diimmonium compound represented by general formula (VI):

wherein R³¹, R³², R³³, R³⁴, R³⁵, R³⁶, R³⁷, and R³⁸ each represent ahydrogen atom or a substituted or unsubstituted alkyl group having 1 to8 carbon atoms; R³⁹, W⁴⁰, R⁴¹, and R⁴² each represent a hydrogen atom, ahalogen atom, a substituted or unsubstituted alkyl group having 1 to 8carbon atoms, or a substituted or unsubstituted amino group, wherein themethylene moiety of the alkyl group may be substituted with —O— or—CH═CH—; and n represents an integer of 1 to
 4. 27. The optical filteraccording to claim 14, wherein the dye cation (C) is a cation of adiimmonium compound represented by general formula (VI):

wherein R³¹, R³², R³³, R³⁴, R³⁵, R³⁶, R³⁷, and R³⁸ each represent ahydrogen atom or a substituted or unsubstituted alkyl group having 1 to8 carbon atoms; R³⁹, R⁴⁰, R⁴¹, and R⁴² each represent a hydrogen atom, ahalogen atom, a substituted or unsubstituted alkyl group having 1 to 8carbon atoms, or a substituted or unsubstituted amino group, wherein themethylene moiety of the alkyl group may be substituted with —O— or—CH═CH—; and n represents an integer of 1 to
 4. 28. The optical filteraccording to claim 13, which is for application to an image display. 29.The optical filter according to claim 14, which is for application to animage display.
 30. The optical filter according to claim 15, which isfor application to an image display.
 31. The optical filter according toclaim 16, which is for application to an image display.